Underwater welding standards, explained

EN ISO 15618-1 — welder qualification for hyperbaric wet welding

EN ISO 15618-1 is the internationally applied qualification standard for underwater welders welding steel in a hyperbaric wet environment. The standard describes, among other things, the test pieces, test conditions, essential variables, acceptance requirements and the range of qualification.

The qualification is tied to the conditions and variables under which the underwater welder was tested. The water depth and the corresponding ambient pressure play an important role here.

To keep the qualification valid, it must be confirmed periodically that the underwater welder has carried out work within the qualified range. This confirmation is provided by the employer, welding supervisor or welding coordinator.

Our welder qualification tests for hyperbaric wet welding are carried out to EN ISO 15618-1 and independently conducted under DNV oversight.

EN ISO 15618-2 — welder qualification for hyperbaric dry welding

EN ISO 15618-2 is the qualification standard for underwater welders and welding operators welding steel in a dry hyperbaric environment. A sealed habitat or work chamber is placed around the weld location, in which the water is displaced and work takes place under elevated ambient pressure.

The standard describes the essential requirements, ranges of qualification, test conditions, acceptance criteria and certification for both underwater welders and operators of mechanised or automated welding processes.

Dry hyperbaric welding is used when high demands are placed on the control and quality of the welded joint, for example for critical repairs, offshore structures and pipelines at greater water depth.

ISO 15614-9 and ISO 15614-10 — qualification of the welding procedure

Not only the underwater welder but also the welding procedure being used must be qualified for the intended work.

ISO 15614-9:2025 describes the qualification of welding procedures for hyperbaric wet welding. The standard applies to production and repair welds and distinguishes weld quality levels A, B and Z. Each level sets its own requirements for the properties and testing of the welded joint.

ISO 15614-10:2005 covers the qualification of welding procedures for dry hyperbaric welding. The standard sets the minimum testing requirements and can also be applied to mechanised and automated welding processes. The welding procedure is qualified within defined limits for the welding conditions applied and the essential variables. This edition was reviewed in 2025 and confirmed as current.

The personal welder qualification (LK) demonstrates that the underwater welder is competent within a defined range. The welding procedure qualification (LMK/WPQR) demonstrates that the chosen welding procedure can produce a welded joint with the required properties under the qualified conditions.

Professional underwater welding work generally requires both: a qualified underwater welder and a qualified welding procedure.

The Hyperbaric Welding Center arranges both qualification tracks under DNV oversight:

• LK: personal qualification of the underwater welder
• LMK/WPQR: qualification of the welding procedure at company level

AWS D3.6M — the American code for underwater welding

AWS D3.6M is the American code for welding structures and components under water, in both wet and dry hyperbaric environments. The code distinguishes three weld classes: Class A, Class B and Class O.

• Class A: weld quality and applications comparable to conventional surface welding
• Class B: intended for less critical applications, with adjusted acceptance criteria
• Class O: meets the requirements of another designated code or specification, supplemented with the relevant requirements of the client

Within AWS D3.6M, too, water depth plays an important role in qualification. The depth at which the test is performed helps determine the qualified depth range of the welder and the welding procedure.

Alongside the qualification route to EN ISO 15618-1, our training programme also prepares underwater welders for qualification to AWS D3.6M. This is particularly relevant for work for international clients, offshore companies and contractors that specify the American code in their project or contract specifications.

AWS currently lists D3.6M:2017 as the published edition of the Underwater Welding Code.

DNV

The Lasinstituut is our specialised partner for examining and qualifying underwater welders and welding procedures. Authorised examiners assess the qualification tests on behalf of DNV in accordance with the applicable standards and certification schemes.

DNV is our standard and preferred certification route. Where a client or project requires a different scheme, qualification and approval to other recognised standards and classification-society rules — such as Lloyd’s Register, ABS or Bureau Veritas — can be arranged on request. We are therefore not limited to a single certification body.

The welder qualification (LK) is personal and demonstrates that the underwater welder has the required practical competence within a defined range of qualification. DNV, as an independent certification body, takes the certification decision and issues the qualification certificate.

The welding procedure qualification (LMK/WPQR) does not relate to one person but to a company’s welding procedure. Testing demonstrates that the welding procedure applied can produce a welded joint with the required quality and properties under the qualified conditions.

Both tracks can be arranged through the Hyperbaric Welding Center:

• LK: qualification and certification of the underwater welder
• LMK/WPQR: qualification and approval of the welding procedure at company level

What does ‘class approved’ mean?

For classed assets, such as ships and offshore structures, additional requirements may apply from a classification society, for example DNV, Lloyd’s Register, ABS or Bureau Veritas.

‘Class approved’ is not a universal certificate that a training centre can issue on its own. The approval always relates to a clearly defined subject, such as:

• a welder qualification;
• a welding procedure qualification;
• a welding workshop or executing company;
• a material, filler material or component;
• specific work within a project.

The applicable classification society determines, based on its own rules and the project specifications, how the qualification is to be assessed. This may take place, for example, by witnessing the qualification test, by document review or by another recognised assessment route.

A professional training and qualification centre provides the necessary foundation for this: a well-prepared underwater welder qualified to the applicable standard, a correct welding procedure and a complete, traceable qualification dossier.

When a client requires additional witnessing or approval by DNV, Lloyd’s Register, ABS or Bureau Veritas for a specific project, this is agreed in advance between the contractor, the client and the classification society concerned.

A qualification to an international standard is therefore not automatically approved for every class and every project. Final acceptance is determined by the applicable rules and the project specifications.

Important: AWS D3.6M is broader than a welder qualification standard alone. The code contains requirements for both underwater welders and welding procedures, and for wet and dry underwater welding.

EN ISO 15618-1 covers the qualification of welder-divers for hyperbaric wet welding. EN ISO 15618-2 covers welder-divers and welding operators for dry hyperbaric welding.

ISO 15614-9 and ISO 15614-10 are welding procedure qualification standards for hyperbaric wet and dry hyperbaric welding respectively.

DNV-ST-F101 and API 1104 are not personal certificates. They are technical codes for pipeline systems and for welding work on pipelines and associated components.